The invention relates to a clutch mechanism. Particularly, but not exclusively, the invention relates to a clutch mechanism for use in conjunction with the brush bar of a vacuum cleaner and the drive therefor.
Upright vacuum cleaners have downwardly directed dirty-air inlets arranged in the cleaner head through which dirty air is sucked into the vacuum cleaner. In the vast majority of cases, a brush bar is rotatably arranged in the mouth of the dirty air inlet so as to agitate the fibres of a carpet over which the vacuum cleaner is passed to release dirt and dust trapped in the carpet. The brush bar is normally rotated by the motor of the vacuum cleaner via a drive belt.
Upright vacuum cleaners are commonly convertible into cleaners which can be used as cylinder cleaners for above-floor cleaning. In this mode of operation, the main part of the cleaner, including the cleaner head, is often left stationery for a period of time with the motor running whilst dirty air is sucked into the vacuum cleaner via a hose or wand. If the brush bar is allowed to continue to brush against the carpet during this time, the carpet can become unnecessarily worn. Many cleaners incorporate devices for automatically lifting the cleaner head and brush bar away from the carpet when the cleaner is put into cylinder mode, but the rotation of the brush bar is not normally stopped since the lifting of the cleaner head prevents the unnecessary brushing of the carpet. A clutch mechanism has been proposed in which the drive belt used to drive the brush bar is shifted onto an idler pulley to disengage the drive when the cleaner is put into the cylinder mode of operation, but this type of mechanism is bulky, expensive to produce and unreliable.
Another difficulty with upright vacuum cleaners is that, on occasion, the brush bar will become jammed. When this happens, the motor can easily overheat and/or the drive belt can become damaged. Some machines are equipped with devices for automatically cutting out the motor when it overheats, but this is not always sufficient warn the user of the cause of the cut out and, when the motor has cooled, the cleaner is switched on again but the problem remains. Furthermore, there is always a risk, with machines of this type, that foreign objects such as children""s fingers can be inserted into the dirty air inlet and serious injury can be caused by a rotating brush bar.
An object of the present invention is to provide a clutch mechanism, particularly a clutch mechanism suitable for use with a rotating brush bar of a vacuum cleaner, which is compact and reliable when used to disengage the drive of the brush bar. Another object is to provide a clutch mechanism which reduces the risk of overheating of the motor or mechanical failure in the event of the torque required to turn the brush bar exceeding a predetermined level. A further object is to provide a clutch mechanism which encourages the user of a vacuum cleaner to remove the cause of the problem when the brush bar becomes jammed.
The invention provides a clutch mechanism. The clutch mechanism includes override means, and is capable of allowing the brush bar to be driven in the engaged position, of disengaging the drive to the brush bar when above-floor cleaning is being carried out, and also of allowing the motor to continue running without overheating or destroying the drive belt (or belts) if the torque required to turn the brush bar exceeds a predetermined level. A vacuum cleaner in which the clutch mechanism is fitted is thereby safer to operate than known cleaners and is less prone to damage or faults which require maintenance or spare parts to be fitted. The cleaner is therefore cheaper to run and more user-friendly.
A preferred embodiment of the invention includes a feature in which belts remain carried by their respective pulleys in the same axial position means that the clutch mechanism can be put into the disengaged position without the need for bulky, unreliable means for transferring one or more belts to an idler pulley. Removing the need for axial movement of either pulley heads to less wear and tear on the components involved and also reduces the likelihood of malfunction.
A further preferred embodiment of the invention produces an override signal when override occurs draws the attention of the user of a vacuum cleaner in which the mechanism is fitted to the fact that the torque required to turn the brush bar exceeds a predetermined value and the need for the cause of the problem to be removed. The override signal is given at all times when the brush bar is jammed or retarded and is not triggered by the operating temperature of the motor. The user of the vacuum cleaner is therefore encouraged to remove the cause of the problem before recommencing cleaning, which is not always the case with cleaners in which the motor cuts out when its operating temperature exceeds a predetermined value when the brush bar is jammed. The invention discourages the user from continuing to use the machine under abnormal or strained conditions. A further advantage is that, when the override signal is audible, an audible warning is given immediately a foreign object such as a child""s fingers is introduced into the dirty air inlet thereby minimizing any delay between an accident occurring and its discovery.